#include <time.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <stdbool.h>

#include <cglm/ivec2.h>
#include <cglm/cam.h>

#define STB_IMAGE_IMPLEMENTATION
#include <stb/stb_image.h>

#if defined(_WIN32) || defined(__WIN32__) || defined(WIN32)
/* include winapi */
#include <Windows.h>
#elif defined(__APPLE__)
/* mac includes */
#elif defined(__linux) || defined(__linux__) || defined(linux)

#include <unistd.h>
#include <sys/sysinfo.h>

#endif

#include <daw/configure.h>

#include <daw/state.h>
#include <daw/daw.h>
#include <daw/utils/btree.h>
#include <daw/utils/hashmap.h>
#include <daw/utils/list.h>

#include <daw/resources.h>

#include <daw/window.h>
#include <daw/rendering.h>
#include <daw/platform_glfw.h>


#define DEFAULT_NUM_PROCS 8

Instance* GLOBAL_PLATFORM = NULL;

input_callback_t* callbacks[128];
usize callbacks_len;

i32 nproc(void) {
  return get_nprocs();
}

void delay( uint64_t us )
{
#if defined(_WIN32) || defined(__WIN32__) || defined(WIN32)
    Sleep( ms );
#else
    struct timespec ts = {
      .tv_sec = (i64)us / 1000000,
      .tv_nsec = ((i64)us * 1000) % 1000000000
    };
    struct timespec rem = {0,0};
    int err = 0;
    while((err = clock_nanosleep(CLOCK_MONOTONIC, 0, &ts, &rem))) {
      switch (err) {
        case EINTR:
          WARN("clock_nanosleep didn't sleep full duration: interrupted.");
          break;
        case EINVAL:
          WARN("clock_nanosleep didn't sleep full duration: invalid argument.");
          break;
        case ENOTSUP:
          WARN("clock_nanosleep didn't sleep full duration: unsupported clock.");
          break;
        default:
          WARN("clock_nanosleep didn't sleep full duration!");
          break;
      }
      ts = rem;
      rem = (struct timespec){0,0};
    }
#endif
}

i32 cmp_int(const void* a, const void* b) {
  const i32* x = a;
  const i32* y = b;

  return *x - *y;
}

/* Creates the window, initializes IO, Rendering, Fonts and engine-specific
 * resources. */
Instance* engine_init(const char* windowtitle, i32 windowWidth, i32 windowHeight,
                      const u32 flags,
                      const usize initial_memory) {

  INFO("Engine version " ENGINE_VERSION);


#if defined(__linux) || defined(__linux__) || defined(linux)
  {
    pid_t pid = getpid();
    INFO("Starting with pid %lu", pid);
  }
#endif
  ivec2 windowsize = {windowWidth, windowHeight};

  Instance* p = (Instance*)calloc(1, sizeof(Instance));
  Window* w = (Window*)calloc(1, sizeof(Window));

  /* initialize resources */
  Resources* resources = calloc(1, sizeof(Resources));

  // Until we've gotten rid of this global, it is important to set it before
  // `window_new`.
  GLOBAL_PLATFORM = p;

  w = Window_new(&Platform_GLFW, windowtitle,
      WINDOW_FRAMEWORK_GLFW, WINDOW_RENDERER_OPENGL,
      (ivec2){windowsize[0], windowsize[1]}, flags);

  p->window = w;
  p->quit = false;

  p->resources = resources;

  p->frame = 0;
#ifdef _DEBUG
  engine_fps_max(p, 30);
#else
  engine_fps_max(p, 300);
#endif

  p->mem = memory_new(initial_memory);

  INFO("Available cores: %d", nproc());

#ifdef DAW_BUILD_HOTRELOAD

#define State(name)                                                            \
  if (!State_reload(STATE_##name, p->window->bindings, p->window->bindings_len)) {             \
    ERROR("Failed to reload shared object file for state %s", #name);          \
  };

#include <states/list_of_states.h>
#undef State

#endif

  return p;
}


i32 engine_run(Instance* p, StateType initial_state, void* state_arg) {

  Shader default_quad_shader = init_default_shader();
  RenderObject default_quad_renderobject;

  if (p == NULL) {
    ERROR("Platform is uninitialized.\n");
    INFO("initialize with `engine_init`");
    return -1;
  }

  memory* mem = p->mem;

  StateType state = initial_state;

  Window* w = p->window;

  {
    u64 state_init_time = get_time();
    State_init(state, p->window, mem, state_arg);

    r_reset_pipeline(w);
    // TODO: Both the shader & renderobject should only be created here if it is
    // overwritten in Instance->Window.
    // TODO: Add default quad & renderobject to Instance->Window. Should allow
    // for customization.
    default_quad_renderobject = init_default_renderobject(w, default_quad_shader);

    INFO("Initializing state \"%s\" took %.1fns", StateTypeStr[state],
         (get_time() - state_init_time));
  }

  u64 frame_end = get_time();

  // Update ticks
  u64 ticks = 0;

  StateType (*update_func)(Window *restrict, void*, f64) = State_updateFunc(state);

  u64 last_fps_measurement = frame_end;
  u64 last_fps_ticks = 0;

  /* The target frametime measured in μs */
  const u32 fps_cap = p->fps_target > 0 ? 1000000 / p->fps_target : 0;

  u64 measurement_total[10];
  u64 measurement_rendering[10];
  u64 measurement_idle[10];

  memset(measurement_total, 0, sizeof(u64) * 10);
  memset(measurement_rendering, 0, sizeof(u64) * 10);
  memset(measurement_idle, 0, sizeof(u64) * 10);

  /* Main loop */
  do {
    /* frame_start is μs since engine was initialized */
    const u64 frame_start = get_time();

    /* dt measured in μs */
    const u64 dt = frame_start - frame_end;
    measurement_total[ticks%10] = dt;

    /* Delta is relative to FPS cap */
    //const f64 delta = (f64)dt / (f64)fps_cap;

    /* Events */
    Platform_GLFW.window_poll();
    i_flush_bindings(dt, callbacks_len, callbacks, mem->data);

    /* Update */
    StateType next_state;
    next_state = update_func(p->window, (void*)(mem->data), dt);

    if (next_state != STATE_null) {
      if (next_state == STATE_quit) break;

      window_reset_drawing();

      void* retval = State_free(state, mem);
      memory_clear(mem);

      i_ctx_reset();

      // Reset camera to default camera
      free(w->render_targets);

      state = next_state;
      update_func = State_updateFunc(state);
      {
        u64 state_init_time = get_time();
        State_init(state, p->window, mem, retval);

        r_reset_pipeline(w);
        default_quad_renderobject = init_default_renderobject(w, default_quad_shader);

        INFO("Initializing state \"%s\" took %.1fns", StateTypeStr[state],
             (get_time() - state_init_time));
      }
    } else {

      /* Render */
      const u64 rendertime_begin  = get_time();
      render_begin(p->window);
      render_present(p->window, &default_quad_renderobject);
      measurement_rendering[ticks%10] = get_time() - rendertime_begin;

      /* Regulate FPS */
      frame_end = get_time();
      const i64 fps_diff = fps_cap - (i64)(frame_end - frame_start);

      if (fps_diff > 0) {
        const u64 idletime_begin  = get_time();
        delay((u64)fps_diff);
        measurement_idle[ticks%10] = get_time() - idletime_begin;
      }

      frame_end = frame_start;

      /* Print stats */
      const u64 dt_measurement = frame_end - last_fps_measurement;

      /* only make measurements once a second */
      if (dt_measurement > 1000000) {

        double avg_total = 0;
        double avg_rendering = 0;
        double avg_idle = 0;

        for (int i = 0; i < 10; i++) {
          avg_total += measurement_total[i];
          avg_rendering += measurement_rendering[i];
          avg_idle += measurement_idle[i];
        }
        avg_total /= 10.0;
        avg_rendering /= 10.0;
        avg_idle /= 10.0;

        printf("  FPS: %.1f"
               "\tticks: %lu"
               "\tdt: %.3fms"
               "\trendertime: %.3fms"
               "\tidle: %.3fms"
               "\n"
            , ((f64)(ticks - last_fps_ticks)) / ((f64)dt_measurement / 1000000.0)
            , ticks
            , (double)avg_total / 1000.0
            , (double)avg_rendering / 1000.0
            , (double)avg_idle / 1000.0
            );

        last_fps_measurement = frame_end;
        last_fps_ticks = ticks;
      }
    }

    ticks++;
  } while(
      !Platform_GLFW.window_should_close(p->window)
      && state != STATE_quit
  );

  return 0;
}

void engine_stop(Instance* p) {
  if (p == NULL) return;

  //{ /* Deallocate resources */
  //  struct Resources* r = (struct Resources*)p->data;
  //  if (r != NULL) {
  //    /* Destroy textures */
  //    for (usize i = 0; i < r->textures_len; i++) {
  //      if (r->textures[i] != NULL) {
  //        r->textures[i] = NULL;
  //      }
  //    }
  //    free(r->textures);

  //    /* Destroy Fonts */
  //  }
  //}

  Platform_GLFW.window_destroy(p->window);
  free(p->resources);
}

/* Set the maximum framerate */
void engine_fps_max(Instance* p, u16 cap) {
  LOG("Setting max fps to %llu", cap);
  p->fps_target = cap;
}

usize f_get_sz(FILE* f) {
  if (f == NULL) {
    ERROR("File was null!");
    return 0;
  }

  const isize pos = ftell(f);
  if (pos == -1) {
    ERROR("Failed to determine file size (%d): %s", errno, strerror(errno));
    return 0;
  }

  const i32 err = fseek(f, 0, SEEK_END);
  if (err != 0) {
    if (err == ESPIPE) {
      ERROR("File is a pipe");
    } else {
      ERROR("Failed to determine file size!");
    }
    return 0;
  }

  const isize size = ftell(f);

  if (size == -1) {
    ERROR("Failed to determine file size (%d): %s", errno, strerror(errno));
    return 0;
  }

  // Reset the position to the position prior to calling f_get_sz
  fseek(f, pos, SEEK_SET);

  return (usize)size;
}